1. Field of the Invention
The present invention pertains to a method for disposing of certain organic and metallic waste materials resulting from the production and refining of hydrocarbons by adsorption or ion exchange of these materials onto bentonite particles in a water slurry and the injection of the waste slurry into subterranean earth formations through disposal wells.
2. Background
The continuing need to deal with waste materials resulting from the production and refining of hydrocarbons as well as waste materials which develop through the use of hydrocarbon products has resulted in the development of disposal methods wherein the waste material is injected into a disposal zone in a subterranean earth formation through one or more injection wells, which disposal zone has relatively low in situ stress and, preferably, is bounded by zones which have higher in-situ stresses. In this way the waste materials may be disposed of by fracturing the disposal zone and containing the waste material in the fracture space. In some instances the disposal zone may be capable of a form of fluidization or disaggregation to the extent that the particles of waste material may be commingled with the formation particles to fill the void spaces therebetween.
U.S. patent application Ser. No. 08/234,531 filed Apr. 28, 1994 by Paul A. Fletcher and assigned to the assignee of the present invention, discloses and claims a method of disposing of solids waste materials, including naturally occurring radioactive materials, into a fractured disposal zone of an earth formation by forming the fracture using a fracturing fluid and then lining the fracture faces with a sealant or with a permeability reducing material such as sodium bentonite or a similar clay having superior impermeabilization properties. A waste slurry may then be injected into the fracture to occupy the fracture space between the opposed layers of bentonite "filter cake" which have effectively sealed the fracture faces to substantially prevent the migration of waste material into the matrix of the formation disposal zone.
However, prior disposal methods do not take advantage of an important characteristic of bentonite clay and similar clays, such as montmorillonite, which is the ability of these clays, particularly in an aqueous solution, to readily exchange loosely held cations with many metallic cations. In addition, many organic compounds, including those resulting from the production and refining of hydrocarbon fluids can be adsorbed between the sheetlike molecular structure of bentonite and related clay materials. Accordingly, by mixing bentonite and water with metal and organic waste materials or by adding bentonite to an aqueous solution of such waste materials, these contaminants would be fixed to the adsorbent clay as a further containment factor when the clay slurries are injected into subterranean disposal zones. It is to this end that the present invention has been developed with a view to providing a method for disposing of certain metallic and organic waste materials, particularly those developed as a result of the production and refining of hydrocarbon fluids.